Being a mom is hard work. Luckily for Charlize Theron in "Tully," she gets help in the form of a night nanny played by Mackenzie Davis.

In the new full-length trailer, Theron's Marlo is exhausted. She has three kids, including a newborn, with her husband (Ron Livingston). And she reaches a breaking point after spilling breast milk, dropping a phone onto her baby, and getting quizzed about her post-pregnancy body by her two other children.

"Your twenties are great. But then your thirties come around the corner like a garbage truck at 5 a.m.," Marlo sighs.

Her brother (Mark Duplass) suggests a night nanny and thus arrives Tully, like a real-life Mary Poppins to save the day.

"Tully" marks the third collaboration for director Jason Reitman and writer Diablo Cody, who previously teamed up on "Juno" and "Young Adult" (which starred Theron). And much like those movies, "Tully" looks like a blend of mature humor, realistically mundane drama, and sharp performances.

"Tully" opens in theaters April 20.